1 Introduction
In recent years, with the rapid development of China's petroleum industry, the number of domestic AC variable frequency electric drive drilling rigs equipped by Daqing Oilfield Drilling Engineering Company has increased year by year. Most of the frequency converters equipped with these electric drive drilling rigs are 6se70 series frequency converters produced by German Siemens Company. Type rigs are equipped with frequency converters of different numbers and different powers. The internal structure of Siemens 6se70 series frequency converters widely used in petroleum drilling rigs is introduced in detail below, the main classification and causes of failures are analyzed, and corresponding maintenance methods and examples are given.
2 Basic information
Figure 1 is a schematic diagram of the zj50 / 4500db electric drive rig [1]. The power system is composed of 4 800kw diesel generator sets connected in parallel, and the electrical energy is concentrated on the AC bus. The rig turntable is driven by an AC variable frequency motor, and the winch is driven by 2 AC frequency conversion motors are driven together, and each motor is controlled by an independent inverter. The inverter model is 6se7036-5hg62-3ba0 and the power is 630kw. The three mud pumps are driven by three motors and controlled by independent inverters. It is 6se7141-2hj62-3ba0, the power is 1200kw, the drilling motor is 45kw, and its drive inverter model is: 6se7090-0xx84-0ab0.
In the daily operation of the drilling rig, although the inverter itself has perfect monitoring and protection functions, in actual use, it will still fail due to various reasons and cannot operate normally, which will affect drilling production. We gradually mastered the internal structure of the inverter during the use and maintenance process, and guided the maintenance and repair work according to the inverter structure. Figure 2 is a schematic diagram of the structure of 6se7036-5hg62-3ba0 inverter.
The inverter consists of three control cabinets [2], which are switch cabinet, rectifier cabinet and inverter cabinet. Figure 2 shows the names of the main components in the cabinet and the specifications and models of the control board. The switchgear contains components such as reactors, isolating switches, and fuses.
In the rectifier cabinet, there are thyristor bridges, three 6sy7010-0ab51 for the upper thyristor, three 6sy7010-0ab52 for the lower thyristor, the model 6se7041-8gk85-0ha0 control board provides thyristor trigger, voltage , Current, SCR temperature detection and other functions. Cur is the central control board of the rectifier cabinet, providing functions such as parameter setting, protection, and external interface. The pmu parameter setting unit provides functions such as parameter display and setting.
The selection of the braking unit and braking resistor can be determined according to the load characteristics. For example, when the winch is lowered, the motor is in the state of power generation, the inverter must be equipped with a high-power braking unit and braking resistor, and the zj50 / 3150db rig is equipped with 10 200kw The braking unit and resistor can absorb the high energy generated when lowering the drilling tool.
The inverter cabinet contains an igbt inverter bridge. Figure 3 is a schematic diagram. Outside the igbt inverter bridge is a capacitor group. The model of the igbt trigger board is 6se7038-6gl84-1bg2. Fiber optic communication is used to isolate the trigger board from the control circuit. Interface The board provides a trigger optical fiber interface circuit. The cuvc vector control board is the core control board of the inverter. It has functions such as parameter setting, vector control, protection, and interface. The pmu parameter setting unit provides parameter display and setting functions.
3 Main faults of Siemens inverter
The main faults of Siemens inverters are divided into two categories:
3.1 Failures that occur when the software and hardware are intact
It is a fault caused by factors such as parameter setting, power supply voltage frequency, temperature, load, communication, hardware connection and other factors when the inverter's own software and hardware are intact. Siemens inverter has perfect fault and alarm prompts, which can be well distinguished These failures. details as follows:
(1) Frequency conversion failure caused by parameter setting and peripheral component failure. This kind of fault can check whether there is an error in the parameter setting, for example: the parameter setting of p554 is incorrect and the inverter cannot start. In addition, check whether the peripheral devices are normal. Due to the frequent relocation of drilling equipment, broken control lines, damaged plugs, and damaged control switches often occur, these parts should be carefully checked;
(2) Undervoltage, overvoltage, underfrequency and overfrequency faults. This type of failure is mainly caused by the failure of the external power supply, and a few failures are caused by damage to the detection circuit. Most drilling rigs use their own generator sets for power supply, which causes the inverter to malfunction due to the power generation frequency and voltage being lower than the upper or lower limit required by the inverter. The generator set should be repaired first. If the frequency is too low, it is generally caused by a fault of the diesel engine. If the voltage is too low or too high, it is caused by a fault of the generator.
(3) Overload fault. Inverter overload is caused by too short acceleration time, excessive DC braking amount, or too low grid voltage. Generally, the fault can be solved by extending the acceleration time, extending the braking time, and solving the grid voltage. The overload of the motor may be caused by stuck pipe, too fast lifting under heavy load, etc.
(4) Overcurrent fault. External causes: Sudden overload of the motor causes excessive current caused by overcurrent; the insulation between the motor and the motor cable between each phase or each ground is damaged, causing a short circuit between turns or phase to ground, resulting in overcurrent; if the frequency converter is equipped with a speed measuring encoder When the speed feedback signal is lost or abnormal, it will also cause overcurrent. At this time, the encoder and its cable need to be checked. The reason of the inverter itself: parameter setting problems and inverter hardware problems. In the event of an overcurrent fault, first use a clamp ammeter to measure the output current of the inverter to see if the output current is balanced. If the output is unbalanced, there is a problem with the internal components of the inverter.
3.2 Inverter hardware failure
Inverter hardware failure is divided into control system and power component failure.
(1) The control system is faulty. The control board itself fails. Due to the failure of electronic components on the control board, the main control board of the inverter cabinet cuvc, the main control board of the rectifier cabinet cur board, etc. are often damaged. The replacement method is used for maintenance. In addition, failures caused by peripheral devices are often caused by high-voltage electricity in the external control system, which causes damage to the interface circuit of the control board;
(2) Power Siemens inverter also has clear fault display for most hardware faults, which provides great convenience for user maintenance work. This article will give examples.
4 Siemens inverter repair example
4.1 e is displayed on the inverter cabinet pmu
(1) Failure phenomenon
After the inverter is powered on, the inverter pmu displays e. After pressing the p key, there is no response, the inverter cannot be started, and the fault cannot be reset.
(2) Failure analysis and treatment
First check the power supply, measure the 24v between pin 1 and pin 2 on the x101 terminal block of the cuvc board, eliminate the voltage fault of the control system, remove the cuvc board, and carefully observe the above components. It is found that the components burned near the x101 terminal, suspected to be external The control line is mixed with high voltage. After careful inspection of the external circuit, it was found that the control line was connected to high voltage due to insulation damage, which caused the cuvc board to burn out. After eliminating the external fault, the inverter can work normally after replacing the cuvc board. From this failure, it can be seen that if the control board is not burnt out, it should be replaced immediately. Be sure to find out the cause of the failure, otherwise it will cause unnecessary losses.
4.2 f005 is displayed on the rectifier cabinet pmu
(1) Failure phenomenon
In drilling production, when the load increases, the frequency converter suddenly stops working, and the rectifier cabinet reports the f005 fault code. F005 is the power frequency greater than 65hz or less than 45hz.
(2) Failure analysis and treatment
This type of fault generally occurs on the zj30 / 1700db rig, because the rig uses a single 750kw generator set, due to diesel engine failure, the speed of the diesel engine is reduced to less than 1350 rpm under heavy load, and the power frequency is lower than 45hz, resulting in frequency conversion The inverter cannot be used normally. After the diesel engine is repaired, the inverter works normally.
4.3 R03 cabinet reports f031 fault
(1) Failure phenomenon
The rectifier cabinet reported f031 failure, and the frequency conversion could not be started. After inspection, it was found that the second insurance 560a from the left of the rectifier cabinet was broken, and the four insurances of the inverter cabinet 500a were all broken.
(2) Failure analysis and treatment
The meaning of f031 fault code is: the SCR branch fuse is damaged, first do the appearance inspection and measure the SCR, igbt and other parts with a multimeter, the inspection result is normal. After replacing the insurance, re-energize, start the inverter, after the motor runs at 20hz, the four insurances of the inverter cabinet are completely broken, the second of the rectifier cabinet insurance, the fifth is broken, check the motor and the inverter again, the measurement results are all normal At this time, the maintenance work is in trouble, and then continue to replace the insurance to observe. After starting the frequency conversion, it is found that the DC busbar connection between the inverter cabinet and the rectifier cabinet has a fire phenomenon. After inspection, the bolts at the busbar connection are loose, and the bolts are replaced. After that, the inverter works normally. From this failure, it can be seen that because the drilling rig needs to be moved continuously, the fasteners in the inverter cabinet are loose, and the inspection of the key connection parts should be strengthened in the daily maintenance of the inverter cabinet.
4.4 The f011 fault code is displayed on the inverter cabinet pmu
(1) Failure phenomenon
The f011 fault code is displayed on the inverter cabinet pmu. The meaning of f011 is that the inverter is shut down due to overcurrent. Under normal circumstances, the f011 fault can be eliminated by reset operation, but this time it cannot be reset. The f011 fault is always displayed after the inverter is powered on and cannot be eliminated.
(2) Failure analysis and treatment
The fault is generally caused by the following reasons: First, the output of the inverter has a short circuit or ground fault; second, the load is in an overload state. First disconnect the frequency converter and motor cable, and perform insulation test on the motor. The test result is normal and the motor fault is eliminated. Next, check the inverter inverter cabinet igbt inverter circuit, remove the three capacitor groups, check igbt with a multimeter, because there is a freewheeling diode in parallel in igbt, use the multimeter to measure the diode function to measure the emitter and collector, if the positive and negative parameters Normally, igbt is not damaged according to experience. If there is a short circuit or open circuit, the igbt must be replaced. After measurement, the two igbt power tubes on the upper part of the u phase are all damaged, the trigger board is damaged, and the inverter resumes normal operation after replacing the components.
5 Conclusion
From these years of Siemens inverter experience, the following points of maintenance are summarized. First of all, the inverter should be given a good external environment, including stable power supply voltage, frequency, appropriate temperature and humidity [3]. Secondly, the inverter load should be properly reduced, and a certain margin should be set for the maximum torque and maximum current when setting parameters, which can greatly extend the service life of the inverter. For example, our company's zj30 / 1700db drilling rig burned igbt and other power devices frequently for a period of time. Igbt is expensive and causes great losses. After adjusting the maximum working current p128 parameter of the inverter to 600a, we eliminated the phenomenon of burning igbt. Finally, regular maintenance should be performed to remove dust from the inverter and tighten loose parts. In short, the above maintenance and repair work are to play the greater role of the inverter, increase the service life of the inverter, reduce the failure rate of the inverter, so that the inverter can better serve oilfield drilling production.
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